The relay carpet: Ubiquitous two-way relaying in cooperative cellular networks

We consider the up- as well as downlink of a cellular network with multi-user multiple-input multiple-output (MIMO) communication and propose to turn the entire network into a two-hop network where a large amount of relays assist the bidirectional communication. To this end, many two-way relays are spread over the entire area of the network. In addition to introducing the concept of ubiquitous relaying, different two-way relaying protocols are developed, for amplify-and-forward (AF) as well as decode-and-forward (DF) relays. The goal is to efficiently apply two-way relaying to interference limited cellular networks. To achieve this, relaying is combined with a simple form of base station (BS) cooperation that allows canceling some interference terms. The relays are used to reduce the complexity at the terminal nodes and to improve the overall performance by distributed interference management. Our results show that the proposed concept can offer significant gains compared to a conventional multi-user MIMO strategy without relays.